The invention relates to apparatus the purpose of which is to prevent the return of atomized water into dental surgery instruments of the type having separate lines for air and water.
Given the ease with which infection is transmitted, especially via the bloodstream, it is of paramount importance that surgical instruments of all kinds be sterilized to avoid the spread of disease. This requirement is particularly important in the field of dentistry; numerous patients are treated each day, and it is well known that the oral cavity affords one of the easiest paths for the spread of infection.
Numerous devices or apparatus exist currently for the sterilization of single instruments (probes, implements etc.) that are brought into direct contact either with the teeth or with infectious media.
Sterilization is more problematic, however, in the case of power driven dental instruments, or rather of permanent systems and their associated parts, especially high speed drills and similar equipment, inasmuch as these are provided with two separate fluid lines for the supply of water and air; each such line is controlled by shut-off means, located remote from the instrument in most cases.
Operating the shut-off control, the dentist can cause the flow of air and water to cease without difficulty: whilst this presents no problem where the air is concerned, the outlet of the other line continues to drip water which, with the implement still in the oral cavity or suspended in mid-air nearby, constitutes a source of annoyance for the patient. Accordingly, means are adopted, installed at a given point along the water supply line, that will generate a marginally negative pressure on activation of the shut-off means and thus draw the water back into the line, preventing the formation of a drip.
Such a remedy creates drawbacks from the hygiene standpoint however; by generating suction in order to eliminate drips, it happens that spray previously atomized and still lingering (doubtless infected) in the oral cavity, is similarly drawn back through the instrument and into the water line.
The drawback in question can be counteracted with a conventional device by means of which it is possible to disinfect an instrument, or rather, the spray circuit of the system, following each session of treatment; this is effected by filling the spray circuit with a liquid disinfectant that is left to stand for a given duration, according to whether a swift cleansing operation or full sterilization is required, before being flushed out with a rinsing liquid.
Whilst such a method is valid enough in terms of end results, a certain amount of time is required between one patient and the next, in order to effect the disinfection/sterilization procedure.
The majority of equipment pedestals installed in modern dental surgeries incorporate an additional `chip-air` facility, generally associated with the drill control pedal, which causes air only to emerge from the handgrip of the drill at a point adjacent to the cutting bit; the chip-air control by-passes the main solenoid operated shut-off valve governing the supply of air to the turbine, so that a burst of air can be produced at random (the drill being idle) and for the duration required, in order to clear the treatment area before and after drilling, without the need to discard the drill and take up a separate air instrument. Such an arrangement is disclosed, for instance, in GB No. 1166665.
In another system, disclosed in EP No. 042267, the chip-air control is connected to the drill foot pedal via a timer circuit, in such a way that when the pedal is released, closing the main solenoid operated air and water control valves, the chip control will cut in automatically and produce a burst of air from the handgrip for a set time lapse, of duration (2 . . . 3 seconds) sufficient to clear the treatment area.
The object of the invention is one of overcoming hygiene problems that arise when suction is generated in the manner aforementioned, whilst avoiding the adoption of additional media, hence avoiding any extra lapse of time that might be dictated by their use.